Demetrious Johnson has worse resume than GSP, Silva, Jones (for sure) and maybe few others. He is in position where he is because he was lucky at judges scorecards in WEC and early UFC days.
Anderson Silva for example defended belt 11 times (including Lutter fight) and he had better win streak against good 205-ers like former champ Griffin.
Demetrious right now is clearly the best 125er, but Joe B is injured (tore ACL), Borg isnt real contender, he's too young and he missed weight two times. So if one of the best (no 1/2/3) in 135 is sure that he can make the weight and this fight makes sense Demetrious should accept that.
He's clearly ducking Dillashaw, but I think he must take this fight cause otherwise Dana wont book him any fight at 125 and maybe even he's gonna shout this division, 125ers are not draws and never will be.